We thus define and use onset spectrum similarity, which is designed to represent the similarity based on the onset part of sounds in the spectrum domain. As illustrated in REF , it is measured by i) applying median-filtering based drum extraction [1]} which enhances onsets (with a FFT size of 1024 and median filter length of 31 on both axes), ii) converting to multi-resolution CQTs (constant-Q transform) for both \(x\)  and \(\hat{x}\) , and then iii) calculating the mean absolute difference between them.
